Corrected four-unit photographic objective comprising two half systems enclosing thediaphragm



lStAKUH KUUI SR (0' I Ever/.1305 XHIJLE WW-M W1 P93. 3, 1953 A. w.TRONNIER 2,627,205

CORRECTED FOUR-UNIT PHOTOGRAPHIC OBJECTIVE COMPRISING TWO HALF SYSTEMSENCLOSING THE DIAPHRAGM 2 SHEETS-SHEET 1 Filed Dec. 28, 1950 m m mm H wm M Z I A 5w w mp Rr my lm z Rf 1 6 Rr m m R Rf m I I R Rf BY Wa vATTORNEYS b'tARCH ROOF 7" f Feb. 3, 1953 A. w. TRONNIER 7,205

' CORRECTED FOUR-UNIT PHOTOGRAPHIC OBJECTIVE COMPRISING TWO HALF SYSTEMSENCLOSING THE DIAPHRAGM Filed D60. 28, 1950 2 SHEETS-SHEET 2 "O. IO

INVE NTOR ALBRECHT WILHELM TRONNIER BY m m ATTORNEYS Patented Feb. 3,1953 otHKUH KUUI CORRECTED FOUR-'UNIT PHOTOGRAPHIC OBJECTIVE COMPRISINGTWO HALF SYS- TEMS ENCLOSING THE DIAPHRAGM Albrecht Wilhelm Tronnier,Gottingen, Germany, assignor to Voigtlander &. Sohn Aktiengesellschaft,Braunschweig, Germany, a corporation of- Germany Application December28, 1950, Serial No. 203,180 In Switzerland January 13, 1950 Claims.(Cl. 88-57) This invention relates to a photographic objective of themodified Gauss-type, which has high light-transmitting capacity, iscorrected spherically, chromatically, astigmatically and for coma and isdistinguished by a substantial improve ment of the lateral correction incomparison with known objectives of the beforementioned type.

The main object of the present invention is to provide a photographicobjective of the above mentioned type in which an improved simultaneouscombined effect of correction for coma and anastigmatic image fieldflatness with small zonal aberrations is attained by a specificdistribution of the refractive indices of the lens elements incombination with a specific distribution of the lens curvatures.

Numerous other objects, advantages and features of this invention areset forth in the following description and the annexed drawings, whichinclude some examples of the invention, to which the invention is notlimited.

The photographic objective of high light-transmitting capacity accordingto the present invention is contemplated for taking photographicpictures and for projection, and is corrected spherically,chromatically, astigmatically, and for coma. The objective according tothis invention belongs to a modified Gauss-type. It consists of a sys-:

tem of four individual structural lens units, the" centralair-space ofwhich serves as the diaphragn'i space. In this system, the two outerlens units have a distinct converging effect and consist preferably ofindividual. and, in this caseuncemented, positive lenses. The two innerlens units of the system are composed of two members and have altogethera distinct diverging effect. These two inner units are enclosed by the,two outer units in the following manner: the radii of curvature'of theouter lens surfaces of the two inner units, 1. e. the units adjacent thediaphragm, have such values and are convex toward the respective outerunits in such a manner that, on the one hand, the diverging surfaces ofhighest dioptric effect are turned toward the diaphragm in both halvesof the system, and, on'

' rection of zonal aberrations in combination with a strong curvature ofthe astigmatic image shells.

It has now been found that a considerable improvement with regard to thesimultaneous correction with small zonal aberrations, of both kinds ofaberrations and a combination of both types of correction can beattained according to thepresent invention by combining a specificdistribution of refractive indices within the dioptrically highlyeffective lenses of the two lens units which follow the diaphragm andare located on the side of the shorter conjugate'with the simultaneousapplication of the curvatures according to the invention, of the twoinner lens units of the objective system, enclosing the diaphragm.

In order to clearly explain the invention, the four units of the presentmodification of the Gauss-type objective are denoted in the encloseddrawings in the order of their position I, II, III, IV and theindividual elements of the units consisting of more than one element aredenoted'by an index consisting of a small letter of the alphabet (forexample In, In or 1m, etc.). Furthermore, the glasses used arecharacterized by their mean refractive indices consecutively numberedstarting at the side of proceeding toward the side of the shorterconjugate (fdr example m, m, m etc.). In order to identify the radii ofcurvature, they are denoted by an index f if in their unit they are onthe side of the longer conjugate, i. e. on the front side in the meaningof the photographic picture. while the radii of curvature which are intheir unit on the rear side in the meaning of the photographic picture,i. e. on the side of the shorter conjugate. are denoted by an index r.

The photographic objective according to the present invention has thefollowing characteristies:

The two inner lens units (II and III) which enclose the diaphragm andhave all together a diverging eflect, have, according to the invention.such curvature that their two outer radii turned toward the adjacentouter units I and IV--i. e. radii R 11, and R,m have values, the sum ofwhich is positive and clearly greater than zero;

show a continuous increase in the direction of the shorter conjugate, i.e. in the meaning of the photographic picture, in the lenses adjacentthe image side, starting at the center of the systhe longer conjugateand Q moreover, the refractive indices of the lens glasses tem, saidincrease being characterized, on the one hand, in that the differencebetween the arithmetic mean value of the refractive indices of theglasses of the diverging lenses (11b and IIL) enclosing the diaphragm,and the refractive index of the outer lens (IV) turned away from thediaphragm, is distinctly greater than 0.0370, and, on the other hand,simultaneously each individual step of this specific increase of therefractive indices of these glasses from to m and from 11.5 to m, isplainly greater than Using the above explained reference symbols,

, the characteristics of my present invention can be expressed asfollows:

I ,II,+R,1I1;,

By denoting the arithmetical mean of the refractive indices of the twodiverging lenses IIb and 11h enclosing the diaphragm, by

the above combined conditions (B1) and (B2) can also be expressed asfollows: I

For one half of a Gauss-type objective, and also for a lens positionfollowing the diaphragm, a sequence of refractive indices increasingfrom the' diaphragm in the direction of the light, has been suggested inthe German Patent No. 439,556. However, it was not recognized then thatthecombination of (a) a particularly strong and progressive increase ofthe refractive indices with (b) the above outlined distribution of theouter curvatures of the inner units of the total objective, enclosingthe diaphragm is necessary in order to obtain the simultaneous combinedefiect of correction for coma and anastigmatic image field flatness withsmall zonal aberrations. This new combination according to my inventionresults in the elimination of disadvantages of known photographicobjectives of the type here in question and in an objective of new andimproved structure.

In the appended drawings, Figure 1 is a general a structuralillustration of the invention and shows the reference numerals used inthe present application. Figure 2 illustrates an objective of lowerlight-transmitting capacity according to the present invention,.in whichthe two inner units 11 and n consist of cemented lenses. Figure 3illustrates an objective of higher lighttransmitting capacity, accordingto the invention. Figure 4 shows the curve of meridional coma in theform of zonal image height aberrations of a Gauss-type objectivecorresponding to the state. of prior art, while Figure 5 shows thecorresponding aberrations of the example of my invention for the sameinclination of the prinsipal rays on the side of the object and for thesame cross-section of rays.

The objective shown in conventional manner in axial section in Figure 2,is contemplated for reproduction purposes and represents a projectorobjective of a medium-sized image angle, having a relative aperture of 1:2.7 at a useful image field extension of about 50.

The constructive details of the example illustrated in Figure 3, areshown in the following table. In this example, the inner unit II, whichis composed of two elements, arranged on the side of, the longerconjugate and precedes the diaphragm in the meaning of the photographicpicture, consists of two uncemented individual lenses of opposite power,which are separated by a meniscus-shaped air layer. The relativeaperture of this objective shown in Figure 3 by way of example, amountsto 122.3, and its useful image field amounts to 50.

In Figure 5, the division of the axis of abscissas is equal to that inFigure 4, and the division of the axis of ordinates has the samemagnitude of intervals as in Figure 4.

In conformity with the following table, in the drawings R denotes theradii of curvature and d the thickness of the lenses, the distances ofwhich in the air are denoted a. The refractive indices of the glassesused are stated for the blue light -of the Fraunhofer line F with a wavelength of 4861 AE, while the color dispersion of these glasses ischaracterized by the Abb number v. The diaphragm located between theinner units It and III is denoted B. The paraxial intersectional width'of the objective, determining the length of the shorter conjugate, forobjects at infinite distance, referred to rays near the axis, is denotedThe data of this example refer to a focal length of 1, while therespective sections along the lens axis in Figure 3 are-illustratedv fora focal length of f= mm. in natural size.

tStHKUl'I KUU Numerical example +0 (iv-0.06108 111-11360 -60.3 R r=+l.78419 d1=0. 07290 11 -1. 66758 "-57.0 R 4=+l. 08963 R +0 27 G180. ail

ds=0. 04138 Ila=l.63245 7 -86. 2 R a=+0. 27540 b =0. 08807 ua=0. 18423diaphragm space d ==0.03941 m=-1.06045 r -33.9 R i+1. 78419 R n= Rs d=0. 08079 m=-l. 66782 50. 9 Rw=-0. 40089 1 B 3 =0. 00191 su- I tic-=0.05911 1la=L 70254 "-53. 5 Ru= -0. 62343 The above figures show thefollowing:

The figure +0.03822 is clearly greater than zero and is plainlypositive, thus corresponding to condition A.

Furthermore,

The conditions B1 and B2 are met as follows:

(B1) 126 n: 1.70254 1.64645 0.05609 i. e. clearly greater than 0.0370.The individual steps in the increase of refractive indices are:

(B2) 125 7L2 1.66782 1.64645 0.02137,1. e. clearly greater than 0.0185;simultaneously, 7Z6 n5 1.70254 1.66782 0.03472, 1. e. clearly greaterthan 0.0185.

The arithmetical mean of the refractive indices 12:, m of the two innernegative lenses is higher than 1.635. The radii of curvature of theindividual refractive surfaces are in the following ranges:

wherein R1, R2 denote the radii of curvature of the successive lenssurfaces counting from the front and F denotes the equivalent focallength of the total objective.

The focal length of the individual structural wherein f1, 12,. f4 1c arethe focal lengths of said individual structural lens units counting fromthe front.

An important improvement attained by the objective of the presentinvention is demonstrated by the curves shown in Figures 4 and 5.

The curve in Figure 4 shows the meridional coma in the form of zonalimage height aberrations in an objective ofa relative aperture of 1:2and focal length of mm., which belongs to the class of modifiedGauss-type objectives here in. question, consists of four lens unitscomprising altogether six lenses and represents the latest state of theart prior to the present invention. (See H. Zollner, Foto-Kino-Technik,No. 3/1949, Figure 2(0).) In this curve, tangential coma is shown for anangle of inclination of 19, the abscissas corresponding to the height ofthe rays in a plane passing through the vertex of the front surface ofthe objective, perpendicularly to the optical axis. The axis ofcoordinates corresponds to the highest incident ray, in Figure 4.

As a comparison, Figure 5 shows the corresponding aberration curve inthe case of an objective according to the present Figure 3 and the abovetable, for an angle of inclination of 16 54' 11".

In Figures 4 and 5 each, the axis of abscissas is denoted AA and theaxis of ordinates BB. The curve of tangential coma in Figure 4 is de-'noted 01 and the curve of the corresponding aberration in Figure 5 isdenoted C2.

Calculation of the aberration curves of Figures 4 and 5 shows that thepear-shaped disc or image produced under the conditions stated as aresult of coma in the above mentioned objective of the prior art, has aheight of 0.295 mm., while the pear-shaped disc produced in theobjective of the present invention under the stated equal conditions,has a height of 0.146 mm. only.

In the objectives compared, the aberration curves show a similar course,and, therefore, the form of their pear-shaped discs is likewise similar,and, in view of the equal section of rays, the in tensity of light isproportional to the surface area. Therefore, the comparable ratio ofintensities is, with very close approximation, proportional to the ratioof squares of the heights of the pearshaped discs of zonal aberration.

In the above comparison, the ratio of the heights is 7 and the ratio ofintensities is This means thatunder edual conditions the effectivecross-section of the pear-shaped disc in the case of an objectiveembodying the present invention, amounts to 24.5% only, in comparisonwith similar objective representing the latest state of the art prior tothe present invention, or, in other words, the objective of the presentinvention is capable of showing four times smaller details than saidobjective of the prior art.

In the appended drawings, in denotes the distance between the diaphragmand the adjacent front member (I and II) on the side of the majorconjugate and b: denotes the distance between the diaphragmand the rearmember (III and IV) on the side of the major conjugate.

It will be understood that the present invention is not limited to thespecific materials, structures, values and other specific detailsdescribed above and illustrated in the drawings and may be carried outwith various modifications without departing from the scope of theinvention as dethe dioptrically most effective diverging surfaces,

i. e. the inner surfaces adjacent the diaphragm of said unit's amacentthe diaphragm, are turned toward the diaphragm in both halves of thesystem, andi the dioptrically most effective converging surfaces of thepositive elements in the two halves of the system, i. e. the outersurface of each outerlconverging unit in the two halves of the objectiveand the outer surface of each of the two units enclosing the diaphragm,are turned away from the diaphragm; the dioptrically most. efiectiveconverging surfaces, which limit the inner units enclosing the diaphragmon the side turned away from the diaphragm, in both halves of thesystem, being shaped in such a manner that the sum of their radii isclearly greater than zero and thus has a plainly positive value;furthermore, the refractive indices of the lens glasses showing acontinuous increase in the direction of the shorter conjugate, i. e. inthe meaning of the photographic picture, in the lenses adjacent theimage side, said increase starting at the center of wherein R1, R2denote the radii of curvature of the successive lens surfaces countingfrom the front and F denotes the equivalent focal length of the totalobjective.

2. Photographic objective of high light-transmitting capacity,comprising two halves of a system enclosing a diaphragm; each of saidhalf systems being composed of (a) a unit adjacent the diaphragm,comprising two'a'djacent lens elements of opposite power, and (b) aconverging unit turned away from the diaphragm; wherein the dioptricallymost effective diverging surfaces, i. e. the inner surfaces adjacent thediaphragm of said units adjacent the diaphragm, are turned toward thediaphragm in both halves of the system, and the dioptrically mosteffective converging surfaces of the positive elements in the two halvesof the system, i. e. the outer surface of each outer converging unit inthe two halves of the objective and the outer surface of each of the twounits enclosing the diaphragm, are turned away from the diaphragm; thedioptrically most effective converging surfaces, which limit the in-'ner units enclosing the diaphragm on the side turned away from thediaphragm, in both halves of the system, being shaped in such a mannerthat the sum of their radii is clearly greater than zero and thus has aplainly positive value; furthermore, the refractive indices of the lensglasses showing a continuous increase in the direction of the shorterconjugate, i. e. in the meaning of the photographic picture, in thelenses adjacent the image side, said increase starting at the center ofthe system, in such a manner that the difference between the refractiveindex of the outer lens arranged on the image side and turned away fromthe diaphragm and the arithmetical mean of the refractive indices of theglasses of the individual diverging lens elements enclosing thediaphragm,

' is distinctly greater than 0.0370 and simultanethe system, in such amanner that the difference between the refractive index of the outerlens arranged on the image side and turned away from the diaphragm andthe arithmetical mean of the refractive indices of the glasses of theindividual ously each and every individual step of this specificincrease of the refractive indices is greater than 0.0185; the radii ofcurvature of the indi vidual refractive surfaces being in the followingranges:

0.4 F R1 0.8 F

wherein R1, R2 denote the radii of curvature of the successive lenssurfaces counting from the front and F denotes the equivalent focallength of the total objective; the focal lengths of the individualstructural lens units being in the following ranges:

wherein f1, 2 f4, and f6 are the focal lengths of said individualstructural lens units counting from the front.

StAKUH RUOi 3. Photographic objective of high light-transmittingcapacity, comprising two halves of a system enclosing a centrallyarranged diaphragm; each of said half-systems being composed of (a) aunit adjacent the diaphragm, comprising two adjacent lens elements ofopposite power, and (b) a converging lens turned away from thediaphragm; wherein the dioptrically most eflective divergingsurfaces, 1. e. the inner surfaces adjacent the diaphragm. of said unitsadjacent the diaphragm, are turned toward the diaphragm in both halvesof the system, and the dioptrically most effective converging surfacesof the positive elements in the two halves of the system, i. e. theouter surface of each outer converging lens in both halves of theobjectives and the outer surface of each of the two lens units enclosingthe diaphragm, are turned away from the diaphragm; the refractiveindicesof the lens glasses showing a continuous increase starting at the centerof the objective, in the direction of the shorter conjugate, i. e. inthe meaning of the photographic picture, in the lenses arranged on theimage side, in such manner that the difference between the refractiveindex of the outer lens arranged on the image side and turned away fromthe diaphragm, and the arithmetical mean of the refractive indices ofthe glasses of the individual diverging lens elements adjacent to andenclosing the diaphragm, is distinctly greater than 0.0370, andsimultaneously each and every individual step of this specific increaseof the refractive indices is greater than 0.0185, and, furthermore, inat least three of the four converging lenses of the objective, therefractive indices for the yellow d-line of the heliumspectrum arehigher than 1.62 and, simultaneously, the arithmetical mean of therefractive indices of all lenses of the objective, is likewise higherthan 1.62; the dioptrically most efiective. converging surfaces, whichlimit the inner units'enclosing the diaphragm on the sides turned awayfrom the diaphragm, in both halves of the system, being shaped in suchmanner that the sum of their radii of curvature is clearly greater thanzero and has a positive value, and the ratio of the radius of curvatureof the first convex lens surface, in the direction of light, to theradius of curvature of the convex outer surface, which limits. in thedirection of the object, the composite lens group preceding thediaphragm, being smaller than 1.550; the radii of curvature of theindividual refractive surfaces being in the following ranges:

wherein R1, R2 of the successive lens surfaces counting from the frontand F denotes the equivalent focal length of the total objective.

4. Photographic objective of high light-transmitting capacity,comprising two halves of a system enclosing a centrally arrangeddiaphragm; each of said half systems being composed of (a) a unitadjacent the diaphragm, comprising two ad- 10 jacent lens elements ofopposite power, and (b) a converging lens turned away from thediaphragm; wherein the dioptrically most effective divergingsurfaces, 1. e. the inner surfaces adjacent the dia-'- phragm, of saidunits adjacent the diaphragm", are turned toward the diaphragm in bothhalves of the system, and the dioptrically most effective convergingsurfaces of the positive elements in the two halves of the system, i. e.the outer surface of each outer converging lens in both halves of theobjectives and the outer surface of each of the two lens units enclosingthe diaphragm, are turned away from the diaphragm; the refractiveindices of the lens glasses showing a continuous increase starting atthe center of the objective, in the direction of the shorter conjugate,i. e. in the meaning of the photographic picture, in the lenses arrangedon the image side, in such manner that the difference between therefractive index of the outer lens arranged on the image side and turnedaway from the diaphragm, and the arithmetical mean of the refractiveindices of the glasses of the individual diverging lens elementsadjacent to and enclosing the diaphragm, is disdenote the radii ofcurvature tinctly greater than 0.0370, and simultaneously each and everyindividual step of this specific: 1 increase of the refractive indicesis greater than 0.0185, and, furthermore, in at least three of the fourconverging lenses of the objective, the refractive indices for theyellow d-line of the helium spectrum are higher than 1.62 and,simultaneously, the arithmetical mean of the refractive indices of alllenses of the objective, is likewise higher than 1.62; the dioptricallymost effective converging surfacea'whi'ch limit the inner unitsenclosing the diaphragm on the sides turned away from the diaphragm.in'both halves of the system, being shaped in such manner that the sumof their radii of curvature is clearly greater than zero and has apositive value, and the ratio of the radius of curvature of the firstconvex lens surface, in the direction of light, to the radius mcurvatureof the convex outer surface, which limits, in the direction oftheobject, the composite lens group preceding the diaphragm, being smallerthan 1.550; the radii of curvature of the individual refractive surfacesbeing in the following ranges:

wherein f1, fz,,, f4, and fa are the focal lengths of said individualstructural lens units counting from the front.

5. Photographic objective of high light-trans- 1 l' mitting capacity,comprising two halves of a system enclosing a centrally arrangeddiaphragm; each of said half systems being composed of (a) a unitadjacent the diaphragm, comprising two ad- 12 with a wave length of 4861AB, :11, n are the Abb numbers of the individual lens elements and theobjective has a focal length of 1.0, a relative aperture of 1:2.3 and aparaxial intersectional Jacent lens elements of opposite power, and (b)a 5 width of 0.698:

converging lens turned away from the diaphragm; wherein the dioptricallymost effective diverging surfaces, i. e. the inner surfaces adjacent thediaphragm, of said units adjacent the diaphragm, are turned toward thediaphragm in both halves of the system, and the dioptrically mosteffective converging surfaces of the positive elements in the two halvesof the system, i. e; the outer surface of each outer converging lens inboth halves of the objectives and the outer surface of each of the twolens units enclosing the diaphragm, are

tumedaway from the diaphragm; said objective having the numerical dataset forth in the followingtable, wherein R1, R2 denote theradii ofcurvature of the successive lens surfaces count-. ing from the front,d1, d2 the axial thicknesses of the individual lens elements, 01, az

the distances in air, n1, n2 the refractive indices for the blue lightof the Fraunhofer line F V ALBRECHT WILHIELM TRONNIER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,955,591 Lee Apr. 17, 19342,117,252 Lee May 10, 1938 2,194,413 Warmisham et al. Mar. 19, 1940FOREIGN PATENTS I Number Country Date 1 439,556 Germany Jan. 13. 1927423,468 Great Britain Feb. 1, 1935 427,008 Great Britain Apr. 12, 1935665,520 Germany Sept; 2'7, 1938

